The United States and Japan will step up their defence cooperation to deal with the threat from nuclear-armed North Korea as tensions in East Asia remain high, officials from the two allies said on Thursday.

NSW jails consider lockdown searches

Random cell searches during lockdown are under consideration in NSW jails following an inquest into the overdose death of a female inmate.

Tracy Lee Brannigan was locked inside a high-risk cell at Dillwynia Women's Correctional Centre on Sydney's outskirts on the afternoon of February 24 last year.

The following morning her cell mate woke at 5am to find the 41-year-old's body slumped on the floor.

In handing down the findings of an inquest into her death, Deputy State Coroner Paul MacMahon said on Monday the availability of drugs in prisons across NSW was an "endemic problem".

He recommended Corrective Services consider implementing random searches of cells at or shortly after lockdown, as drug taking appeared to happen after inmates were locked in for the night.

These should particularly be geared towards known or suspected drug users, he said.

Corrective Services NSW Commissioner Peter Severin said in a statement that he would: "seriously consider that as a potential extra measure to our current approach of detection, deterrence and treatment".

The comments come after the inquest heard how drugs were often thrown over the fence into Dillwynia in tennis balls.

Brannigan, police told the inquest, had formed a lesbian relationship with several female inmates, including her cell mate Lauren Ironside, who gave her drugs in return for sex.

On the night of Brannigan's death the pair had a "drug party" in their cell with heroin and prescription drugs, to celebrate Ironside's bail the following day to a rehabilitation centre.

Director of Women in Prison Advocacy Network Kat Armstrong told the inquest Brannigan was "all over the place" when she saw her on the afternoon of February 24 and that it was obvious the 41-year-old was on drugs.

But Mr MacMahon rejected that Brannigan was drug affected at this point.

Instead he found that it was "more likely than not" that Brannigan administered heroin to herself shortly after being locked in her cell.

Public Interest Advocacy Centre (PIAC) CEO Edward Santow said random searches of cells at lockdown would help save lives.

Speaking after the inquest, Brannigan's mother Sandra said she was "very happy" about the recommendation.